Full spine and full leg radiographic examinations require images that are longer than the length of normal-sized radiographic films. The problem is circumvented by two approaches. The first approach uses an extra long, non-standard film. This approach is expensive and inconvenient. The second approach uses several normal-size films for exposure and then tape the sub-images together (see U.S. Pat. Nos. 3,725,703 and 3,774,703). Computed Radiography (CR) has the same problem. The problem is circumvented by either using an elongated CR plate (U.S. Pat. No. 5,130,542) or by using several CR plates for imaging, and then using digital image processing to stitch the sub-images together (U.S. Pat. Nos. 5,111,045, 5,986,279 and EPO 919856A1).
With the advent of flat panel digital radiography (DR), it is natural to apply the technology to full spine/leg imaging. Various patents teach the assembly of smaller sensor arrays to form a large sensor (U.S. Pat. Nos. 5,105,087, 4,467,342, and 4,755,686). However, DR sensors are expensive. Thus the DR assembly approach is economically prohibitive. One patent teaches the use of a moving sensor to detect fan beam X-ray in CT scan (U.S. Pat. No. 4,873,708). The approach takes the scanned signals and constructs a sliced image of the body. U.S. Pat. Nos. 4,613,983 and 5,123,056 disclosure systems for imaging a human subject on a table including an X-ray source, a table and an image intensifier tube. Either the table or X-ray source and table are moved to produce a series of overlapping electronic images which are combined into an elongated image for display or printing. Another patent teaches a moveable X-ray cassette holder design.
The field of DR is expanding rapidly. Physicians order full spine and full leg imaging routinely for scoliosis patients and for leg length, angulation and deformity measurements. It is therefore necessary to provide an economically feasible capability for acquiring images using flat panel digital radiography that can be used for subsequent construction of full spine and long bone images.